Refining the Simple Performance Tester for Use in Routine Practice (2008) / Chapter Skim
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Appendix B - Revised Simple Performance Test System Specification
Appendix B - Revised Simple Performance Test System Specification
Pages 65-137
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From page 65... ...
65 A P P E N D I X B Revised Simple Performance Test System Specification
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From page 66... ...
...71 4.0 Simple Performance Test System ...................................................................................72 5.0 Compression Loading Machine ......................................................................................73 6.0 Loading Platens ........................................................................................................... ....74 7.0 Load Measuring System .................................................................................................75 8.0 Deflection Measuring System .........................................................................................75 9.0 Specimen Deformation Measuring System ....................................................................75 10.0 Confining Pressure System ...........................................................................................77 11.0 Environmental Chamber ...............................................................................................78 12.0 Computer Control and Data Acquisition ......................................................................78 13.0 Computations .............................................................................................................
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From page 67... ...
The test may be conducted with or without confining pressure. The resulting axial strain is measured as a function of time and numerically differentiated to calculate the flow time.
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a. Axial Strain in Flow Time Test.
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b. Rate of Change of Permanent Axial Strain.
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compressive stress of various frequencies. The applied stresses and resulting axial strains are measured as a function of time and used to calculate the dynamic modulus and phase angle.
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3.0 Test Specimens 3.1 Test specimens for the Simple Performance Test System will be cylindrical meeting the following requirements.
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This information is provided for design of the Simple Performance Test system. 4.0 Simple Performance Test System 4.1 The Simple Performance Test System shall be a complete, fully integrated testing system meeting the requirements of these specifications and having the capability to perform the Flow Time, Flow Number, and Dynamic Modulus tests described in Annexes A, B, and C and AASHTO TP62.
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The requirements for each of the simple performance tests are listed below. Test Type of Loading Capacity Rate Flow Time Ramp, constant 10 kN (2.25 kips)
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5.5 For the Flow Time and Flow Number Tests, the loading platens shall remain parallel during loading. For the Dynamic Modulus Test, the load shall be applied to the specimen through a ball or swivel joint.
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load. 9.0 Specimen Deformation Measuring System 9.1 The Simple Performance Test System shall include a glued gauge point system for measuring deformations on the specimen over a gauge length of 70 mm (2.76 in)
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Submit data showing the alternative system produces the same modulus and phase angles as the standard system on asphalt concrete specimens tested over the stiffness range of 150 to 10,000 MPa (20,000 to 2,200,000 psi)
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10.8 The confining pressure system shall be designed for rapid installation of the test specimen in the confining cell and subsequent equilibration of the chamber temperature to the target test temperature. Specimen instrumentation, installation, application of confining pressure, and temperature equilibration shall take no longer than 3 minutes over the complete range of temperatures.
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From page 78... ...
12.0 Computer Control and Data Acquisition 12.1 The Simple Performance Test System shall be controlled from a Personal Computer operating software specifically designed to conduct the Flow Time, Flow Number, and Dynamic Modulus Tests described in Annexes A, B, C, and AASHTO TP62; and to analyze data in accordance with Section 13. 12.2 The Simple Performance Test System Software shall provide the option for user selection of SI or US Customary units.
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From page 79... ...
12.3.4 The control system shall terminate the test and return the deviator stress and confining pressure to zero when the axial strain exceeds 5 percent or the maximum user specified test duration time is exceeded. Note: in Project 9-19, flow time criteria will be developed for mixtures as a function of climate, and traffic level.
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From page 80... ...
12.3.9 If at any time during the creep loading portion of the test, the deviator stress, confining pressure, or temperature exceed the tolerances listed below, the Flow Time Test Software shall display a warning and indicate the parameter that exceeded the control tolerance. The test shall continue and the software shall include this warning in the data file and the hard copy output.
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12.4 Flow Number Test Control and Data Acquisition 12.4.1 The control system shall control the deviator stress, and the confining pressure within the tolerances specified in Sections 5 and 10.2 12.4.2 The control system shall be capable of applying an initial contact stress, then testing the specimen with the user specified cyclic deviator stress. 12.4.3 The data acquisition and control system shall provide the user the ability to select the sampling interval as a whole number of load cycles.
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From page 82... ...
Target Confining Stress 0.1 CONFINING PRESSURE +/- 2% CONTACT DEVIATOR STRESS +/- 2% TIME, SEC ST RE SS , k Pa 0.9 REPEATED DEVIATOR STRESS +/- 2% P(1)
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From page 83... ...
The rate of change of permanent axial strain shall be computed in accordance with the algorithm presented in Section 13. 12.4.10 If at any time during the test, the peak deviator stress, standard error of the applied load, confining pressure, or temperature exceed the tolerances listed below, the Flow Number Test Software shall display a warning and indicate the parameter that exceeded the control tolerance.
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10. Cycle and corresponding measured peak deviator stress, computed load standard error, measured contact stress, measured confining pressure, measured temperature, measured permanent axial strain, and computed rate of change of permanent strain.
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6. Review dynamic modulus, phase angle, temperature, confining pressure, and data quality statistics (See Section 13)
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The test shall continue and the software shall include this warning in the data file and the hard copy output. Response Tolerance Confining pressure +/- 2 percent of target Temperature +/- 0.5 o C of target Permanent Axial Strain 0.0050 mm/mm 12.5.11 At the end of the user selected sweep of frequencies, the Dynamic Modulus Test software shall display a summary listing the following data for each frequency tested: 1.
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7. Time and corresponding measured axial stress, individual measured axial strains, measured confining pressure, and measured temperature, 8.
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13.1.2 The first step in determining the flow time is to estimate the rate of change (derivative) of the axial strain with respect to time t using a finite-difference DYNAMIC MODULUS STANDARD REPORT Data generated on : 4-Apr-01 Dynamic Modulus, ksi: 45.7 Data exported on : 4-Apr-01 Phase Angle, Deg.: 30.1 Sample ID: FHWA D0 Project: WO 621 System Configuration : Data Quality Indicators: Test Frequency (Hz)
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From page 89... ...
Wh ere: d i /dt = rate of change of strain with respect to time or creep rate at i sec, 1/s i- t = strain at i- t sec i+ t = strain at i+ t sec t = sampling interval 13.1.3 The derivatives calculated in Section 13.1.2 shall then be smoothed by calculating the running average at each point, by adding to the derivative at that point the two values before and two values after that point, and dividing the sum by five: dt d dt d dt d dt i d dt d dt d t i t i t i t i i 2 2 5 1 ' (5) Wh ere: d ' i /dt = smoothed creep rate at i sec, /s d i-2 t /dt = creep rate at i-2 t sec, 1/s d i- t /dt = creep rate at i- t sec, 1/s d i /dt = creep rate at i sec, 1/s d i+ t /dt = creep rate at i+ t sec, 1/s d i+2 t /dt = creep rate at i+2 t sec, 1/s 13.1.4 The flow time is reported as the time at which the minimum value of the smoothed creep rate occurs, and shall be reported to the nearest t seconds.
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i/dN = rate of change of permanent axial strain with respect to cycles or creep rate at cycle i, 1/cycle ( p) i- N = permanent strain at i- N cycles ( p)
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If more than one point share the minimum creep rate, the first such minimum shall be reported as the Flow Number. 13.3 Dynamic Modulus Test 13.3.1 The data produced from the dynamic modulus test at frequency 0 will be in the form of several arrays, one for time [ti]
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array is constructed: n i ji n i ji n i ji n i ji j tY tY tY Y YX 1 0 1 0 1 1 sin' cos' ' ' ' (10) Where Yj represents the output from one of the three transducers (j=1 for the load cell, j=2 and 3 for the two deformation transducers)
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This produces values for the phase angle, and standard errors for each transducer output. The phase angles given by Equation 13 represent absolute phase angles, that is, j is an arbitrary value indicating the angle at which data collection started.
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Where D is the average absolute phase angle for the deformation transducers, and j is the phase angle for each of the j = 2, 3, …, m deformation transducers. For the typical case, there are one load cell and two deformation transducers, so m = 3, and Equation 17 simply involves summing the phase angle for the two deformation transducers and dividing by two.
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= Average standard error for all deformation transducers, % UA = Uniformity coefficient for deformation amplitude, % U = Uniformity coefficient for deformation phase, degrees 14.0 Calibration and Verification of Dynamic Performance 14.1 Prior to shipment, the complete Simple Performance Test System shall be assembled at the manufacturer's facility and calibrated. This calibration shall include calibration of the computer control and data acquisition electronics/software, static calibration of the load, deflection, specimen deformation, confining pressure and temperature measuring systems; and verification of the dynamic performance of the load and specimen deformation measuring systems.
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14.5 Verification of the dynamic performance of the force and specimen deformation measuring systems shall be performed by loading a proving ring or similar verification device with the specimen deformation measuring system attached. The manufacturer shall be responsible for fabricating the verification device and shall supply it with the Simple Performance Test System.
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Drawings. 17.0 Warranty 17.1 The Simple Performance Test System shall carry a one year on-site warranty.
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98 NCHRP 9-29 Equipment Specification for the Simple Performance Test System Version 2.0 March 26, 2004 Annex A Simple Performance Test System Flow Time Test Adapted From Test Method for Static Creep/Flow Time of Asphalt Concrete Mixtures in Compression NCHRP Report 465, 2002
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. 2.2 Other NCHRP 9-29 Equipment Specification for the Simple Performance Test System 3 Definitions 3.1 Flow Time – Time corresponding to the minimum rate of change of axial strain during a creep test.
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6 Apparatus 6.1 An approved Simple Performance Test System meeting the requirements of NCHRP 929 Equipment Specification for the Simple Performance Test System 6.2 An environmental chamber for conditioning the test specimens to the desired testing temperature. The environmental chamber shall be capable of controlling the temperature of the specimen over a temperature range from 30 to 60 C (85 to 140 F )
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From page 101... ...
8.2.3 Place the specimen and platen assembly in the environmental chamber with the dummy specimen, and monitor the temperature of the dummy specimen to determine when testing can begin. 8.2.4 Turn on the Simple Performance Test System, set the temperature control to the desired testing temperature and allow the testing chamber to equilibrate at the testing temperature for at least one hour.
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9 Calculations 9.1 The calculation of the flow time for individual specimens is performed automatically by the Simple Performance Test System software. 9.2 Compute the average and standard deviation of the flow times for the three specimens tested.
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103 NCHRP 9-29 Equipment Specification for the Simple Performance Test System Version 2.0 March 26, 2004 Annex B Simple Performance Test System Flow Number Test Adapted From Test Method for Repeated Load Testing of Asphalt Concrete Mixtures in Uniaxial Compression NCHRP Report 465, 2002
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2. Referenced Documents 2.1 AASHTO Standards PPXX Standard Practice for Permanent Deformation and Fatigue Evaluation of HMA Using the Simple Performance Test System (To be developed)
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6. Apparatus 6.1 An approved Simple Performance Test System meeting the requirements of NCHRP 9-29 Equipment Specification for the Simple Performance Test System 6.2 An environmental chamber for conditioning the test specimens to the desired testing temperature.
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8.1.3 Turn on the Simple Performance Test System, set the temperature control to the desired testing temperature and allow the testing chamber to equilibrate at the testing temperature for at least one hour. 8.1.4 When the dummy specimen and the testing chamber reach the target temperature, open the testing chamber, remove a test specimen and platen assembly, and quickly place it in the testing chamber.
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From page 107... ...
8.2.4 Turn on the Simple Performance Test System, set the temperature control to the desired testing temperature and allow the testing chamber to equilibrate at the testing temperature for at least one hour. 8.2.5 When the dummy specimen and the testing chamber reach the target temperature, open the testing chamber, remove a test specimen and platen assembly, and quickly place it in the testing chamber.
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10.4 Attach Simple Performance Test System standard reports for individual specimens.
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109 NCHRP 9-29 Equipment Specification for the Simple Performance Test System Version 2.0 March 26, 2004 Annex C Simple Performance Test System Dynamic Modulus Test Adapted From Test Method for Dynamic Modulus of Asphalt Concrete Mixtures for Permanent Deformation and Test Method for Dynamic Modulus of Asphalt Concrete Mixtures for Fatigue Cracking NCHRP Report 465, 2002
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2. Referenced Documents 2.1 AASHTO Standards PPXX Standard Practice for Permanent Deformation and Fatigue Evaluation of HMA Using the Simple Performance Test System (To be developed)
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6. Apparatus 6.1 An approved Simple Performance Test System meeting the requirements of NCHRP 9-29 Equipment Specification for the Simple Performance Test System 6.2 An environmental chamber for conditioning the test specimens to the desired testing temperature.
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The Simple Performance Test System will automatically unload when the test is complete and display test data and data quality indicators. 9.1.9 Review the data quality indicators as discussed in Section 10 of this test method.
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The Simple Performance Test System will automatically unload when the test is complete and display test data and data quality indicators. 9.2.10 Review the data quality indicators as discussed in Section 10 of this test method.
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11.4 Attach Simple Performance Test System standard dynamic modulus summary report.
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115 NCHRP 9-29 Equipment Specification for the Simple Performance Test System Version 2.0 March 26, 2004 Annex D Procedure for Developing a Dynamic Modulus Master Curve for Pavement Structural Design Using The Simple Performance Test System.
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The approach described here is very similar to that contained in AASHTO Provisional Standard TP62-03, "Standard Method of Test for Determining Dynamic Modulus of Hot-Mix Asphalt Concrete Mixtures," except a reduced number of temperatures, an expanded range of frequencies, and an estimate of the limiting maximum modulus are used. The recommended test sequence in AASHTO TP62-03 consists of testing a minimum of 2 replicate specimens at temperatures of –10, 4.4, 21.1, 37.8, and 54.4 C (14, 40, 70, 100, and 130 F)
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Figure 1. Schematic of Master Curve and Shift Factors.
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= shift factor as a function of temperature T = temperature The shift factors are a function of temperature. In the 2002 Design Guide, the shift factors were expressed as a function of the binder viscosity to allow aging over the life of the pavement to be considered using the Global Aging Model developed by Mirza and Witczak (2)
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= shift factor as a function of temperature T = temperature, Rankine A, VTS= viscosity-temperature relationship parameters for RTFOT aging c = fitting parameter Substituting Equation 5 into Equation 2b and the result into Equation 1 yields the form of the dynamic modulus master curve relationship used in the 2002 Design Guide for the development of master curves from laboratory test data.
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From page 120... ...
Through the numerical optimization, the test data are essentially extrapolated to define the limiting minimum and maximum moduli. When information concerning the viscosity-temperature relationship for the binder is not available, a master curve can still be constructed and used to compare materials or used in pavement structural design methods other than the 2002 Design Guide.
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REDUCED TEMPERATURE RANGE To properly fit the master curves in Equations 6 and 8, test data are needed over a range of temperatures. Particularly troublesome is the collection of dynamic modulus test data at low temperatures to define the upper bound of the sigmoidal function (limiting maximum modulus)
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For this wide range of volumetric properties, the limiting maximum modulus varies from about 3,000,000 psi to 3,800,000 psi. These limiting maximum modulus values appear very rational.
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= dynamic modulus t = loading time T = temperature, K Max = limiting maximum modulus , , and aE = fitting parameters The four unknown fitting parameters are still estimated using numerical optimization of the test data, but since the limiting maximum modulus is known, data at low test temperatures are no longer needed. MASTERSOLVE WORKBOOK The computations needed to develop a dynamic modulus master curve are easily performed using the Solver function in Mircosoft EXCEL .
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the fitted master curve and the shifted average modulus data as a function of reduced loading time, (2) the shifted average phase angle data as a function of reduced loading time, (3)
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4. Christensen, D.W., and Anderson, D.A., "Interpretation of Dynamic Mechanical Test Data for Paving Grade Asphalt Cements," Journal of the Association of Asphalt Paving Technologists, Vol.
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126 NCHRP 9-29 Equipment Specification for the Simple Performance Test System Version 2.0 March 26, 2004 Annex E Specification Compliance Test Methods for the Simple Performance Test System
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Transducer Accuracy 8.4 Independent deflection verification (See verification procedures below) Load Mechanism Compliance and Bending 8.5 Measure on steel specimens with various degrees of lack of parallelism Configuration of Specimen Deformation Measuring System 9.1 Visual Gauge Length of Specimen Deformation Measuring System 9.1 Measure Transducer Range 9.2 Independent deflection verification (See verification procedures below)
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Transducer Accuracy 9.4 Independent deflection verification (See verification procedures below) Specimen Deformation System Complexity 9.5 Trial Confining Pressure Range 10.1 and 10.5 Independent pressure verification (See verification procedures below)
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3.0 Deflection and Specimen Deformation Measuring System Static Verification 3.1 Perform verification of the deflection and specimen deformation measuring systems in accordance with ASTM D 6027 Test Method B 3.2 The micrometer used shall conform to the requirements of ASTM E-83.
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3.6 If the readings of the first verification do not meet the specified error tolerance, perform calibration adjustments according to manufacturer's specifications and repeat the applications of measurement to satisfy the error tolerances. 4.0 Confining Pressure Measuring System Verification 4.1 Perform verification of the confining pressure measuring system in accordance with ASTM D-5720.
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6.5 The verification device will also be used to check the phase difference between the load and specimen deformation measuring system. The phase difference shall be less than 1 degree.
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132 NCHRP 9-29 Equipment Specification for the Simple Performance Test System Version 2.0 March 26, 2004 Annex F Minimum Testing Program For Comparison of a Non-Standard Specimen Deformation Measuring System to the Standard Specimen Deformation Measuring System
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Thus a total of 24 specimens will be fabricated and tested. 2.0 Test Specimens 2.1 The testing shall be performed on simple performance test specimens meeting the dimensional tolerances of Section 3.0 of these specifications.
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Specimen Deformation System Standard1 25 (77) 0 Proposed Standard2 25 (77)
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( 2 12 12 i i yy s (F-2) where: y = sample mean s 2 = sample variance yi = measured values 5.0 Statistical Hypothesis Testing 5.1 For each combination of temperature, confining pressure, and frequency of loading test the equality of variances between the standard specimen deformation system and the proposed specimen deformation measuring system using the F-test described below.
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From page 136... ...
5.3 If the results conclude the variance is greater for the proposed measuring for any of the combinations of temperature, confinement, and loading frequency tested, then the proposed measuring system is unacceptable. 5.4 For combinations of temperature, confinement, and loading frequency where equality of variances is confirmed by the hypothesis test in Item 5.1, test the equality of means between the standard specimen deformation system and the proposed specimen deformation measuring system using the t-test described below.
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From page 137... ...
6.4 Summary tables of dynamic modulus, phase angle, and data quality indicators for each combination of temperature, confining pressure, and loading frequency for the two measuring systems. 6.5 Summary tables of the mean and variance of the dynamic modulus and phase angle for each combination of temperature, confining pressure, and loading frequency for the two measuring systems.
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